Fix SDL event initialization and backend context allocation

[kimkulling]

• This initialization is based on an union and will cause undefined behavior.

Summary by CodeRabbit

• Bug Fixes
  • Improved renderer event handling to reduce rare event-processing issues and enhance runtime stability.

[coderabbitai]

Walkthrough

Single change in Renderer::update(const Context &ctx): SDL event local variable initialization changed from value-initialized (SDL_Event event = {};) to default-uninitialized (SDL_Event event;), altering whether event fields are zeroed before being used.

Changes

Cohort / File(s)	Summary
SDL2 Renderer Backend src/backends/sdl2_renderer.cpp	Replaced value-initialized SDL_Event event = {} with default-uninitialized SDL_Event event; in Renderer::update(const Context &ctx), affecting initial contents of the event struct passed to IODevice::update(event).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Refactorings/decouple backend #26: Modifies the same functions in src/backends/sdl2_renderer.cpp, including event handling logic.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title mentions both SDL event initialization and backend context allocation, but the actual changes only affect SDL event initialization (removing value-initialization). The title is broader than the changeset.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bugfix/fix_undefined_behavior

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@src/backends/sdl2_renderer.cpp`:
- Line 282: The line assigning ctx.mBackendCtx = new BackendContext;. has an
accidental trailing '.' after the semicolon which causes a compile error; edit
the assignment where ctx.mBackendCtx is set (new BackendContext) to remove the
extra '.' so the statement ends with just the semicolon and rebuild.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a6897168-df2b-4695-8979-09776e8b2aa1

📥 Commits

Reviewing files that changed from the base of the PR and between 626deb3 and 4ad7714.

📒 Files selected for processing (1)

• src/backends/sdl2_renderer.cpp

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (2)

src/backends/sdl2_renderer.cpp (2)

504-504: ⚠️ Potential issue | 🔴 Critical

Syntax error: int32_t int s is invalid.

This line has an erroneous int keyword that will cause a compilation failure on big-endian systems.

🐛 Proposed fix

-    const int32_t int s = (bytesPerPixel == 4) ? 0 : 8;
+    const int32_t s = (bytesPerPixel == 4) ? 0 : 8;

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/backends/sdl2_renderer.cpp` at line 504, The line declaring s is
malformed ("int32_t int s") causing a compile error; remove the stray "int" and
declare s correctly as a single int32_t initialized from bytesPerPixel (e.g.
replace the broken declaration in src/backends/sdl2_renderer.cpp with a single
declaration of the symbol s using int32_t and the existing ternary using
bytesPerPixel) so the variable s is properly defined on all platforms.

---

472-476: ⚠️ Potential issue | 🟠 Major

Bug: Accessing wrong union member for SDL_MOUSEMOTION events.

For SDL_MOUSEMOTION events, the active union member is event.motion, not event.button. Accessing event.button.x/y instead of event.motion.x/y is technically undefined behavior (accessing inactive union member).

🐛 Proposed fix

             case SDL_MOUSEMOTION:
                 {
-                    const int32_t x = event.button.x;
-                    const int32_t y = event.button.y;
+                    const int32_t x = event.motion.x;
+                    const int32_t y = event.motion.y;
                 } break;

Note: The variables x and y are also currently unused. Consider either removing this case or implementing the mouse motion handling.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/backends/sdl2_renderer.cpp` around lines 472 - 476, The SDL_MOUSEMOTION
case is reading the wrong union member (event.button) which is undefined; change
accesses to use event.motion.x and event.motion.y in the SDL_MOUSEMOTION branch
(or remove the unused x/y locals if motion handling is not needed). Locate the
SDL_MOUSEMOTION switch case in sdl2_renderer.cpp and update the variables (or
drop the case) so the active union member event.motion is used and unused
variables are eliminated or used for actual mouse-move handling.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Outside diff comments:
In `@src/backends/sdl2_renderer.cpp`:
- Line 504: The line declaring s is malformed ("int32_t int s") causing a
compile error; remove the stray "int" and declare s correctly as a single
int32_t initialized from bytesPerPixel (e.g. replace the broken declaration in
src/backends/sdl2_renderer.cpp with a single declaration of the symbol s using
int32_t and the existing ternary using bytesPerPixel) so the variable s is
properly defined on all platforms.
- Around line 472-476: The SDL_MOUSEMOTION case is reading the wrong union
member (event.button) which is undefined; change accesses to use event.motion.x
and event.motion.y in the SDL_MOUSEMOTION branch (or remove the unused x/y
locals if motion handling is not needed). Locate the SDL_MOUSEMOTION switch case
in sdl2_renderer.cpp and update the variables (or drop the case) so the active
union member event.motion is used and unused variables are eliminated or used
for actual mouse-move handling.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 21f1021d-929f-4d39-b122-590ac6ef162f

📥 Commits

Reviewing files that changed from the base of the PR and between 4ad7714 and af08ad9.

📒 Files selected for processing (1)

• src/backends/sdl2_renderer.cpp